# Why ASCII has only 255 codes?

###### Wiki User

###### 2012-08-10 16:26:36

"Answer_to_Why_ASCII_has_only_255_codes" id=

"Answer_to_Why_ASCII_has_only_255_codes">Answer to Why ASCII has

As you know the alphabet has 26 letters. If you include capital

letter that would be 52. There is also lots of punctuation, digits

we end up with 127. But there is other function buttons (example.

Ctrl + Alt + Del) we need to get more space.

If we use 7 binary digits (Computers counting systems is binary)

we end up with 127. That isn't enough to hold all the characters.

So we make it 8 binary digits. The maximum number for 8 binary

digits is 11111111. Which in our counting system is 255.

ASCII is a 7-bit character encoding, so it has only 128 codes: 0

through 127. The upper 128 codes in an 8-bit byte (128 through 255)

are unused and undefined by ASCII, but many ASCII extensions (such

us ISO-8859-1) make use of those unused codes.